The invention relates to a method and an arrangement for communication duration restriction in a telecommunications network, especially in a mobile communications network.
Modern telecommunications networks offer a subscriber several supplementary services in directing a call. Call Forwarding (CF) is a supplementary service which permits a called subscriber to have the network route all incoming calls to a preset number. Call Transfer (CT) is another supplementary service which permits a subscriber to transfer an established incoming or outgoing call to a third party. Such supplementary services pose the threat of fraud, making use of telecommunication services without the intent to pay. Mobile communications networks are especially exposed to fraudulent use. Typically, a fraudulent user applies for a subscription with false identity and with no intention to pay any telephone bills. The most common types of fraud are related to the ability to sell calls, such as forwarded or transferred calls. In such cases, the fraudulent user programs the desired telephone number as the forwarded-to number for the fraudulent subscription, after which the caller pays only for a local call, for example. Without good control large unpaid bills could be produced by calling expensive destinations such as Premium Rate or international numbers. It is very much in the interests of the network operators to detect this misuse and stop it at the earliest possible opportunity.
FIG. 1 of the attached drawing shows a simplified block diagram of the GSM mobile communications system. The mobile station MS is connected via a radio path to a base transceiver station BTS, in FIG. 1, to the base station BTS1. A base station sub-system BSS consists of a base station controller BSC and the base stations BTS controlled by it. A mobile services switching center MSC usually controls several base station controllers BSC and is connected to other mobile services switching centers and a GMSC (Gateway Mobile Services Switching Center). Via the GMSC the GSM network is connected to other networks, such as the PSTN (Public Service Telephone Network), another mobile communication network PLMN, the ISDN network, the intelligent network IN, or the short message service center SMSC. The operation of the entire GSM system is monitored by the operation and maintenance center OMC. Subscriber information of the mobile station MS is stored permanently in the Home Location Register HLR and temporarily in the Visitor Location Register VLR of the area in which the mobile station MS is currently located. Subscriber information contains information on all the services the subscriber is entitled to and the subscriber""s present location. The information as to the location of the mobile station MS is stored in the visitor location register VLR with the accuracy of a Location Area LA.
One method for preventing large unpaid bills is to limit the duration of the calls. In some networks, switching center specific parameters limiting the duration of the calls are used. These limiting parameters are common for all the subscribers and for all types of calls. Therefore, within one MSC all the calls are limited to one hour, for example. When the time limit is reached, the call is released or some other network element specific action is performed, such as giving a report to the operator.
The problem with known fraud prevention methods is that the duration of calls can be restricted only by a default value which is either used for all the calls of all the subscribers or for none. It is not possible to define limiting values on a subscriber basis. Yet the operator has varying needs to monitor the possible fraudulent use of different subscribers. On the other hand, there is the problem of the long duration of certain types of calls, especially to certain destinations.
The object of this invention is to implement effective and flexible prevention of fraudulent use in a telecommunications network on a subscriber basis.
This is achieved through a method and an arrangement according to the invention characterized by what is stated in the independent claims. Special embodiments of the invention are presented in the dependent claims.
The invention is based on the idea that at least one restriction table is created with restriction parameters for monitoring the duration of subscriber""s communication on the basis of the call type and the applicability of this restriction table to individual subscribers is indicated by a status parameter in subscriber specific data. Based on the call type, such as a forwarded or mobile originated call, the correct restriction parameter is retrieved from the restriction table for those subscribers for whom the status parameter is set xe2x80x9conxe2x80x9d and the limiting value included in the restriction parameter is used in detecting and indicating calls of long duration. In one embodiment of the invention the restriction parameters are created to apply on the basis of call type and call direction.
The advantage of the method according to the invention is that the network operator is able to restrict the duration of calls on a call type base. Additionally, restriction can be directed to the subscribers individually. The system provides tools for the operator to monitor and limit the duration of the subscriber""s calls, including transferred and forwarded calls.
Another advantage of the method according to the invention is that the management of the restriction parameters is simple.
The advantage of the arrangement according to the invention is that the subscriber data file is not enlarged to any great extent, but rather only with individual restriction status at the most.